Low Temperature Variable Refrigerant Flow (VRF) with or without Simultaneous Heating and Cooling for Large Commercial Applications
Low Temperature Variable Refrigerant Flow (VRF) Systems: Low Temperature VRF Heating and Cooling vs. Code Minimum HVAC
Variable refrigerant flow systems for large commercial buildings, similar to ID #126, but designed specifically for climates with frequent low temperatures so that auxiliary heat is not needed, or is needed only at very low temperatures.
Item ID: 311
Traditional heat pumps loose their efficiency and ability to work at low outside air temperatures, the actual minimum temperature depending on manufacturer. At low outdoor temperatures, the traditional heat pumps resort to inefficient electric strip heaters. The equipment proposed here, however, is superior as it can still provide heat pump heating (aka, compression heating) at temperatures down around -25 degrees.
This technology can be installed with or without simultaneous heating and cooling. Systems without heat transfer between zones are appropriate in applications where all the zones act similarly, such as an auditorium or a row of classrooms with similar exterior exposures. Systems with heat transfer between zones cost a little more than the system without simultaneous heating and cooling and would be appropriate in an application where some zones are in heat mode while some are in cooling mode, such as an apartment building, office building, etc, with dissimilar exterior exposures and/or dissimilar uses.
Since about 2006, low temperature heat pumps (LTHPs) have been a standard offering in the U.S. from many manufacturers. Unlike standard heat pumps, the cold climate heat pump provides efficient heating capacity even at -25 degrees F. This equipment is also more sturdy, resulting in more reliability.
On new construction, other benefits include reduced building heights since ductwork can be minimized and reduced building electric service and wire sizes since all HVAC is 'soft' start.
Baseline Description: Code minimum HVAC
Baseline Energy Use: 10.5 kWh per year per square foot
The 2009 Commercial Building Stock Assessment gives the actual electrical building EUI's for various types of heating and cooling systems (Table D-EA5). Office buildings with electric heating and cooling have an EUI of 20.1 kWh/sf-year. Office buildings with no electric heating or cooling use only 8.2 kWh/sf-year, indicating that the combined HVAC heating and cooling energy use is 11.9 kWh/sf-year. (For all commercial buildings, the corresponding numbers are 19.9 and 9.4 kWh/sf-year, respectively). Since this technology can be applied to many types of non-office buildings, a baseline energy use of 10.5 kWh/sf-year is assumed (NEEA, 2009).
Manufacturer's Energy Savings Claims:
Currently no data available.
Best Estimate of Energy Savings:
"Typical" Savings: 25%
Low and High Energy Savings: 15% to 40%
Energy Savings Reliability: 5 - Comprehensive Analysis
The efficiency of this ET is 100% at 0 degrees, and 75% at -20 degrees. The baseline is 100% at 20 degrees and 75% at 0 degrees, using strip heat to supplement the code minimum heat pump when it cannot meet the load. The estimate is for a climate that sees outside air temperatures below 20 degrees about 10% of the hours per year.
Energy Use of Emerging Technology:
7.9 kWh per square foot per year
Energy Use of an Emerging Technology is based upon the following algorithm.
Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))
Potential number of units replaced by this technology:
This technology could technically be used for conditioned space in virtually any commercial building, so we are using the total of the entire commercial building stock in the Northwest. The numbers are taken from preliminary updated numbers from the 2013 update to the Commercial Building Stock Assessment (CBSA) using the estimates for 2014 (before the update was completed -- from early January, 2014) multiplied times the percentage of commercial space that is conditioned based on the 2009 CBSA. It is not appropriate for small single-zone buildings, which we approximate as those buildings with less than 5000 sf (10% of all space), nor is it appropriate for buildings with high ceilings, such as big box stores. This is taken to be buildings of those types between about 20,000 and 200,000 sf, or about 50% of retail and grocery space. We can only count electrically-heated buildings for the purposes of BPA savings potential. According to the CBSA, about 30% of commercial buildings are heated with electricity. Finally, the low-temperature heat pumps will mostly apply to BPA heating zones 2 and 3 (greater than 6000 heating degree days), or 20% of the Northwest population. We assume that the commercial space and its characteristics are essentially proportional to the population.
Commercial Floor Space Appropriate for VRF with Internal and External Heat Recovery in Cold Climate Zones
Regional Technical Potential:
| || Total Floor space || -s.f. Warehouse || non-Warehouse || % Conditioned || -% Sm. (>5K) || Applicable Space || 50% Retail & Groc. || Appropriate Space ||Elect. Ht. ||Cold Climate |
| Source || (NEEA, 2014) || (NEEA, 2009 App C) || || || || || (NEEA, 2009 App C) || || || |
| || 3,118,000,000 || 173,000,000 || 2,945,000,000 || 87.0% || 10% || 2,305,935,000 || 240,000,000 || 2,065,935,000 || 619,780,000 || 123,956,000 |
0.33 TWh per year
Regional Technical Potential of an Emerging Technology is calculated as follows:
Baseline Energy Use * Estimate of Energy Savings (either Typical savings OR the high range of savings) * Technical Potential (potential number of units replaced by the Emerging Technology)
Currently no data available.
Simple payback, new construction (years): N/A
Simple payback, retrofit (years): N/A
Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.